1. Field of the Invention
The present invention is relates to a transmitter which includes a speech encoder, which comprises analysis means for determining a plurality of linear prediction coefficients from a speech signal. Such analysis means comprises pitch determining means for determining a fundamental frequency of said speech signal, the analysis means further being arranged for determining an amplitude and a frequency of a plurality of harmonically related sinusoidal signals representing said speech signal from said plurality of linear prediction coefficients and said fundamental frequency.
The present invention also relates to a speech encoder, a speech encoding method and a tangible storage medium comprising a computer program implementing said method.
2. Description of the Related Art
A transmitter according to the preamble is known from EP 259 950.
Such transmitters and speech encoders are used in applications in which speech signals are to be transmitted over a transmission medium with a limited transmission capacity, or stored on storage media with a limited storage capacity. Examples of such applications are the transmission of speech signals over the Internet, the transmission of speech signals from a mobile phone to a base station and vice versa, and storage of speech signals on a CD-ROM, in a solid state memory or on a hard disk drive.
Different operating principles of speech encoders have been tried to achieve a reasonable speech quality at a modest bit rate. In one of these operating principles the speech signal is represented by a plurality of harmonically related sinusoidal signals. The transmitter comprises a speech encoder with analysis means for determining a pitch of the speech signal representing the fundamental frequency of said sinusoidal signals. The analysis means are also arranged for determining the amplitude of said plurality of sinusoidal signals.
The amplitudes of said plurality of sinusoidal signals can be obtained by determining prediction coefficients, calculating a frequency spectrum from said prediction coefficients, and sampling said frequency spectrum at the pitch frequency.
A problem with the known transmitters is that the quality of the reconstructed speech signal is lower than is required.